The world population, now approaching 5.0 billion people, has doubled since 1950. According to present predictions it is expected to double again by the year 2025, and to stabilise at some higher level by the year 2100. Population growth is already stabilising in the developed countries. Almost ail of the future expansion in numbers will therefore take place in the countries of the developing world.
The challenge to the world's cattle population in servicing human needs for milk (and also for meat and work) therefore lies overwhelmingly in developing countries. The huge expansion in demand for milk which will follow from population growth is superimposed on a milk supply position which is already inadequate. Typical annual milk consumption figures for large sectors of the developing world are around 25 kg. per head per year. This contrasts with the 300 kg. per year which is normal in the countries of the developed world.
World cattle numbers are currently 1.2 billion, giving a ratio of approximately four humans to one bovine. Broadly speaking, the developed world has one-third of the cattle, 23% of the people and produces over 80% of the milk. The countries of the developing world (Latin America, Africa and Asia) have three-quarters of the human population, two-thirds of ail the cattle stocks, and produce less than 20% of the milk (Table 1.1). There are some obvious reasons for these great disparities: climate, feed resources, cattle types, degree of economic development. These factors are reflected in productivity levels per cow on the one hand, and consumption patterns per person on the other (Table 1.2).
PERCENT OP WORLD CATTLE, PEOPLEAND MILKPRODUCTIONINDEFRENT REGIONS (FAO, 1982).
|PERCENT OF WORLD|
There is a 10 fold range in milk output per cow, from approximately 500 kg. par annum in Africa and India to over 5000 kg. in North America and Europe. Milk available per person per year varies from less than 10 kg. in China to about 25 kg. in India and Africa, nearly 100 kg. in Latin America, and 300 kg. or more in most developed countries. The world average is 95 kg. per person.
At a world level there are estimated to be somewhat over 200 million dairy cows representing 17% of total cattle stocks. The definition of what is a dairy cow is a rather elastic one, and includes many animals which are only marginally involved in milk production. Throughout the developed world, the total numbers of dairy cows are declining, though total milk production is being maintained. In the developing world, on the other hand, dairy cow numbers have been increasing, at about 3% per annum in Latin America and the Near East, and somewhat more slowly in Asia and Africa. Continued growth in numbers is expected in these areas.
SOME STATIST1CS ON WORLD CATTLEANDDAIRY COWNUMBFFS AND MILK OUTPUT (FAO, 1982).
|Total Cattle||Dairy Cows||Dairy Cows As % cattle||Total Milk||Milk/Cow||Total People||Milk/Person|
In parallel with these broad differences in numbers and productivity of dairy cows between the developed and developing worlds, there is also a major difference in cattle types: Bos taurus breeds being exclusively used in temperate and developed areas, while Bos indicus types predominate numerically throughout most of the developing world (Figure 1.1). The origins of these two broad cattle types predate modem organised breeding programs. The physical, physiological and behavioural differences between the two types arise from the different selection pressures exercised over long periods by the very different physical environments to which they were exposed. These differences have been accentuated within the past century by accelerated selection for high level specialised dairy production in some Bos taurus populations. Within Bos taurus, this has led to the emergence of a few dominant breeds, with an increasing global dominance of Holstein-Friesian types. This process of highly effective selection for dairy function, coupled with increasing concentration on fewer breed types, is continuing.
As various countries in the developing world tackle the challenge of increasing the productivity of their dairy cow populations, it is immediately apparent that the substantial genetic difference in mille production potential between Bos indicus breeds and improved Bos taurus breeds is too large to be ignored. To put this difference in perspective, we could say that the Bos taurus dairy cattle appear to have a genetic potential for milk production 100% higher than that of Bos indicus (see table 18.104.22.168). At the same time, efficient dairy selection schemes produce rates of genetic change of approximately 1% per year. The genetic difference between taurus and indicus types therefore is roughly equivalent to the gain achievable from 100 years of sustained and highly efficient selection within a population.
The most obvious way to exploit this difference would be to simply import Bos taurus cattle to tropical areas. This has been tried on many occasions in the past, generally with unsatisfactory results. Bos taurus types usually fail to produce adequately, and often even to survive, in the face of the multiple challenges of climatic stress, new diseases and parasites, and nutritional insufficiency. In recent decades, some successes have been achieved, particularly in the dry tropics, where great efforts have been made to control disease, improve nutrition, and reduce climatic impact. Nevertheless, the early failures led to considerable disillusionment with Bos taurus types in tropical areas. The result was, particularly in India, the adoption of policies of reliance on development of local breeds.
Figure 1.1 World distribution of dairy cows, showing the approximate limits of Bos Taurus and Bos Indicus predominance.
In the last three decades, the accumulation of new knowledge and new techniques has led to a further shift in opinion on these matters. The availability of artifical insemination has made crossbreeding between Bos taurus and Bos indicus populations very widely possible. The conclusions from a substantial number of crossbreeding trials, summarised later in this report, indicate substantial advantages, even in stressful conditions, for crossbreds between the two types. These questions have been most systematically addressed in India, where the accumulated information has led to a change in national policy, which now is aimed at producing crossbreds between Bos taurus and local Bos indicus breeds on a very large scale (20 million). This strategy is being emulated on a smaller scale in many other countries whose native populations are of Bos indicus type.
The scale of committment of resources to these large crossbreeding schemes is very great. It is also a committment which has to be sustained for many decades into the future. Furthermore, it is essential that these programs are successful, if the challenge of real nutritional need in the developing countries is to be met. Ail of these considerations serve to emphasise the necessity for soundly based decision making in the planning stages of these crossbreeding programs. This requires both the generation and correct interpretation of appropriate experimental and pilot scale data. It also requires a rational planning framework on which to develop practical breeding schemes.